I. Field of the Invention
The present invention relates generally to tool holders.
II. Description of the Prior Art
The previously known tool holders typically comprise an elongated body which is generally cylindrical in crossectional shape. An axial bore is formed in one end of the body and the body is adapted to be rotatably driven about this axis.
The shank of a cutting tool is positioned within the axial bore so that the cutting tool extends generally axially outwardly from one end of the tool holder body. A radial threaded bore is also provided in the body which intersects the axial bore and receives a threaded fastener. Upon tightening of the fastener, the fastener abuts against the shank of the cutting tool and secures the cutting tool to the tool holder body.
Although the axial bore is dimensioned to tightly receive the shank of the cutting tool, of necessity there must be some clearance between the cutting tool shank and its receiving bore on the tool holder body. Consequently, once the threaded fastener is tightened to secure the cutting tool to the tool holder body, the shank of the cutting tool is necessarily forced slightly off center from the axis of the tool holder. Tightening of the threaded fastener also causes slight radial elongation of the tool holder body along the axis of the radial bore.
The above shortcomings of the previously known tool holders all result in "run out" during a machining process using the tool holder. While this run out may be minor and is acceptable for many applications, such run out is unacceptable for other high precision applications. For example, many such high precision applications are found in the aircraft industry.